Morphological failure mechanisms in tensile tests of crosslinked polyurethanes with poorly developed domain structure

Macroscopic failure of polyurethane materials of 30 wt. hard segment content is related to microstructure evolution mechanisms. Topology and functionality f 2 . . . 4 of the polyols are varied. Samples are strained and small angle X ray scattering SAXS patterns are recorded. Only material PU I f 2 passes the tensile test. Material PU Hs a H shaped f 4 polyol with short arms is not nanostructured. PU Hl has long arms. It contains few hard domains placed at random. PU Hl survives longer strain 1.8 than the other short lived materials. Its isolated hard domains are not destroyed during straining. PU X f 4, star shaped develops microfibrils one dimensional 1D correlations among hard domains, as deduced from a chord distribution function CDF analysis. PU I and PU Y are based on 2 and 3 functional polyols. They contain many wellseparated hard domains with one dimensional 3D connectivity. Their arrangement of hard domains evolves identically, but not the population density. In PU I and PU X hard domains fail during straining, in PU Y the interdomain soft phase density decrease